Understanding Acoustic Glazing

06.03.2021

If you are living in a busy area that has lots of noise, the sound of traffic and other outside noises can be disruptive to your daily life and impact on the comfort of your home. If you are suffering from such a noise pollution then an acoustic glazing option for your windows and doors can effectively reduce noise coming from outside. 

What is acoustic laminated glass?

Acoustic laminated glass has an acoustic PVB interlayer placed between laminated glass panes. The acoustic PVB layer delivers significantly improved sound insulation compared to standard laminated glass.

In the acoustic glass, a special resin is present between the two sheets of glass as an interlayer. This construction is not noticeable on looking at the glass. It looks very similar to laminated glass. Acoustic glass is available in varying grades based on the thickness of the interlayer resin. Different grades of glass are more effective at reducing certain frequencies of sound since sound has different wavelengths.

Where can acoustic glass be used? 

Acoustic glass can be used in any application where there is a need to reduce noise pollution, both internally and externally. 

Acoustic glass can serve the need to reduce noise pollution, both internally and externally in any application. Cutting the noise of heavy traffic is a plausible expectation from acoustic glass but to assume it will block 100% of the unwanted sound is way off the mark. Acoustic glass is a great choice if you work from home, have a home office, or simply need silence for any reason. Acoustic glass could be a smart choice for those who live close to an airport or any other busy locale to muffle down high levels of environmental noise.

Things to consider when choosing acoustic glass for your home

Apart from the performance of the windows installed in the building, many other factors affect the levels of external noise entering your home.

  • Define dB Levels Required: High-performance acoustic glazing results in an improved sound reduction in the room. Laminated glass with varying thicknesses offers better performance. But to achieve the best
    performance, it is critical to quantify the desired reduction in sound. This assessment can be
    done with the assistance of a sound engineer. This quantification is then matched with the glass
    type that delivers as per your requirements. 
  • Manufacturing Capabilities: Manufacturing capabilities are important to consider when choosing acoustic glazing for your property. Not every manufacturer will be able to offer different designs in multiple thicknesses, especially when you need more than 24 mm double glazed units. To meet your needs it is
    important to find both the right unit size and optimum thickness chosen for its acoustic value. Thicker acoustic glass is difficult to source from manufacturers, particularly if the design of the window is a traditional one, like a sash window.
  • Window Performance: The performance of the window is one of the key factors that need to be considered before installing acoustic glass. The overall performance like weather testing performance of a window
    unit or assembly is significant because that will affect the noise penetration. Installing acoustic glass in a window with poor performance ratings will serve no purpose. Windows with severe weather ratings are accredited in high-performance schemes.

Using laminated glass for noise reduction

Laminated glass is similar to acoustic glazing in construction. This too consists of two glass panes with an interlayer between the two panes. This interlayer, however, is made from polyvinyl butyral or PVB. PVB has vibration dampening properties. This interlayer and glass thickness determines the effectiveness of your laminated glass. Consolidated results will be affected by the performance of the insulated glass unit or IGU. In an IGU, two panes of glass  are separated with an air space, where the glass could be of any type or thickness. The air present in between glass panes also affects the noise reduction to an extent. Laminated glass is sufficiently effective in facilitating a quiet environment.

Noise reduction glazing uses dissipation and deflection of the sound wave. This is achieved by:

  • Tweaking the thickness of the glass
  • Increasing the interlayers
  • Adding more space between the glass panes

The vibration of sound waves is absorbed by the glass when it hits on the glass surface. Absorption of sound is natural when it passes through any solid object but this absorption is very small in a single thin pane of glass. Double glazing is effective because two panes of glass increase the absorption and the interlayer dampen the transmission of sound waves. 

Disrupting the sound waves is the most effective way to reduce noise and is possible by installing specialist noise reduction glass. In the specialist acoustic glass, two thicknesses of glass panes are joined by PVB laminate in between. This entire structure is very effective in sound dampening and disrupting the sound waves consequently reducing the noise penetration significantly.

Measurement of sound insulation of glass

It is difficult to quantify noise reduction because many factors other than glass come into play. Generally, a noise reduction spectrum for acoustic glazing ranges from 36dB to 52dB for double glazing and may go up to 54dB for triple glazing units. Noise reduction by 25dB is observed in standard double glazed units with two glasses of 4mm each with an air cavity in between.

The calculations may be tricky and confusing for one to understand the mechanics behind soundproof glazing. When noise reduction by a factor of 10dB is observed, it means 50% volume of noise is reduced and a reduction by 40dB gives a 94% drop.

A judgement of the impact of laminated glass can be made by understanding that a 6.5mm thick lamination sheet delivers a 32dB of noise reduction at an average frequency of 400Hz and for a complete IGU of two 4mm standard glass panes with 12 mm air cavity achieve a 27dB reduction.